Poor Washing Performance Can Slow Your Entire Kitchen

When a commercial dishwasher isn't cleaning dishes properly, the problem quickly affects more than just dirty plates. Staff may need to rewash items by hand, service slows down and valuable time is lost during busy periods.

If your commercial dishwasher is leaving food residue, grease, cloudy glasses or poorly cleaned crockery, the cause isn't always obvious. Several different systems work together to produce consistent wash results, and a fault in any one of them can affect cleaning performance.

The good news is that poor washing performance does not always mean the dishwasher requires major repairs. Some issues are related to daily maintenance or operating conditions, while others require professional diagnosis.

This guide explains the common reasons a commercial dishwasher may not be cleaning properly, outlines safe checks operators can perform and explains when professional servicing is recommended.

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How Does a Commercial Dishwasher Clean Effectively?

Commercial dishwashers are designed to clean by combining several factors, including:

• Correct wash water temperature

• Adequate rinse temperature (where applicable)

• Proper water circulation

• Appropriate detergent

• Correct rinse aid dosing

• Effective wash pump performance

• Clean wash arms and jets

• Sufficient water pressure

• Correct loading techniques

If one or more of these factors is affected, overall cleaning performance may decline.

Why Isn't My Commercial Dishwasher Cleaning Properly?

Several different issues can produce similar symptoms.

Common causes include:

• Wash water not reaching the correct operating temperature

• Blocked wash arms or spray jets

• Dirty filters

• Worn or damaged wash pump components

• Incorrect detergent

• Incorrect rinse aid settings

• Hard water or mineral scale

• Overloading the dishwasher

• Poor loading of racks

• Low water pressure

• Mechanical or electrical faults

Correct diagnosis is important because replacing components without identifying the actual cause may not resolve the problem.

Common Causes Explained

Wash Water Temperature Problems

Commercial dishwashers are designed to operate within manufacturer-specified wash and rinse temperatures.

If the dishwasher cannot reach these temperatures, detergent may not perform as intended and grease or food residues may remain on dishes.

If you suspect a heating issue, read our guide on Commercial Dishwasher Not Heating.

Blocked Wash Arms

Wash arms distribute water throughout the dishwasher.

Food particles, labels, broken crockery or mineral deposits can partially block the spray jets, reducing water coverage and leaving some items poorly cleaned.

Regular inspection and cleaning in accordance with the manufacturer's recommendations can help maintain performance.

Dirty Filters

Filters help prevent food debris from entering the wash pump and drainage system.

If filters become heavily soiled, water circulation may be reduced, affecting cleaning performance.

Cleaning filters should form part of the dishwasher's routine daily maintenance.

Wash Pump Problems

The wash pump circulates water through the wash arms.

If the pump becomes worn or develops a mechanical or electrical fault, water circulation may be reduced and dishes may not be cleaned effectively.

Professional testing is usually required to confirm wash pump faults.

Detergent and Rinse Aid

Commercial dishwashers rely on chemicals suited to the machine and application.

Poor washing results may occur if:

• Incorrect detergent is used.

• Detergent concentration is incorrect.

• Rinse aid is empty or incorrectly dosed.

Chemical suppliers or service technicians can help confirm correct dosing.

Hard Water and Mineral Scale

Hard water can contribute to mineral deposits on internal components and glassware.

Scale build-up may reduce heating efficiency and contribute to cloudy glasses or reduced cleaning performance over time.

Appropriate water treatment and preventative maintenance can help reduce these issues.

Incorrect Loading

Overloading racks or placing large items where they obstruct the wash arms may prevent water from reaching all surfaces.

Following the manufacturer's loading recommendations helps maximise wash performance.

Signs Your Commercial Dishwasher Has a Cleaning Performance Problem

Common symptoms include:

• Food residue remaining on plates

• Greasy dishes

• Cloudy or streaky glasses

• White mineral deposits

• Detergent residue

• Water spots

• Items requiring a second wash

• Uneven cleaning across a rack

Several different faults can produce these symptoms, so professional diagnosis may be required.

Safe Checks Before Booking a Repair

Operators can safely check:

✓ Filters are clean.

✓ Wash arms rotate freely.

✓ Spray jets are not visibly blocked.

✓ Detergent and rinse aid containers are full.

✓ The dishwasher has completed its full wash cycle.

✓ Dishes are not overloaded or incorrectly positioned.

✓ A fault code is not displayed.

Do not dismantle pumps, electrical components or control systems.

Why Professional Diagnosis Matters

A commercial dishwasher leaving dishes dirty does not automatically mean the wash pump or heating element has failed.

For example, the same symptom may result from:

• blocked wash arms

• low wash temperature

• incorrect detergent

• rinse aid problems

• poor loading practices

• hard water

• wash pump faults

• electrical faults

Professional diagnosis helps identify the underlying cause before replacement parts are fitted, reducing unnecessary expense and downtime.

Poor Cleaning vs Poor Sanitising – What's the Difference?

Many people assume that if dishes look clean, they have been cleaned properly.

In reality, visible cleanliness and hygienic washing are not always the same thing.

Commercial dishwashers are engineered to operate within manufacturer-specified wash and rinse conditions. These operating conditions are designed to support effective cleaning and, depending on the machine and application, may also contribute to thermal or chemical sanitising processes.

If a dishwasher is not heating correctly, is using incorrect chemicals or is not completing its wash programme as designed, cleaning performance may be affected even when dishes appear visually clean.

If you notice ongoing cleaning problems, professional diagnosis can help identify whether the issue relates to heating, water circulation, chemical dosing or another component of the wash system.

Preventing Poor Cleaning Performance

Routine preventative maintenance helps maintain reliable wash performance.

Depending on the machine, servicing may include:

• Inspecting wash arms

• Cleaning filters

• Testing heating systems

• Checking chemical dosing

• Assessing water quality

• Inspecting pumps

• Testing operating temperatures

• Identifying worn components

Combined with daily operator cleaning, preventative servicing can help extend equipment life and reduce unexpected breakdowns.